Thesis: S.B., Massachusetts Institute of Technology, Department of Materials Science and Engineering, 2015. / Cataloged from PDF version of thesis. / Includes bibliographical references (page 32). / The variability of a nanostructured material's fundamental properties as compared to its bulk state has led to the rich field of nanotechnology and the quest to uncover unique properties of structures at the nanoscale. An active application for these materials is in the nanostructuring of [alpha]-Fe₂O₃ (hematite) for photoelectrochemical (PEC) splitting of water to generate hydrogen. A model of a bubble on a nanorod was developed in this work to facilitate the understanding of equilibrium configurations of oxygen bubbles on a nanostructured hematite electrode. The equilibrium configurations are computed using Surface Evolver, a program which models surfaces shaped by various constraints and forces. A nanorod with a top surface dimension of 100 by 100 nm was the subject of the bulk of this work. The energy of different starting configurations of the bubble and increasing volume of the bubble were compared to that of a free spherical bubble. The energy of the bubble approaches the total surface energy of a free spherical bubble, indicating that a bubble that has nucleated on the surface of a nanorod will approach a shape that has nearly the same energy as a detached spherical bubble. For applications in PEC splitting of water, this result indicates that from an equilibrium and lowest energy perspective, an oxygen bubble could nucleate on the surface of a nanorod, grow in volume, and detach or pinch-off from the nanorod. / by Jennie Olivia Zheng. / S.B.

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2000. / Vita. / Includes bibliographical references (p. 151-155). / Ferromagnetic shape memory alloys (FSMA's) have shown large strains under magnetic field as magnetic variants in the rnartensite rearrange to accommodate the applied field. The theoretical maximum field-induced strain is 6.3% in Ni-Mn-Ga FSMA, and results of 6.1% are presented. These strain establish FSMA's as a new class of active materials with strains much larger than piezoelectric or magnetostrictive actuators. This work looks at Ni-Mn-Ga FSMA and explores the correlation between structure and properties, field induced strain at various stresses, and devices based on this new class of active materials. Martensitic Ni-Mn-Ga was found to have a tetragonal 14/mmm crystal structure with a cla ratio of 1.3 3. Twinning can occur on the { 112} planes. A twin boundary in such a crystal should cause a change of direction in the crystal axes of 7 .1 degrees. This angle was measured at 6.5 degrees in a single crystal of Ni-Mn-Ga. Twin angles and strains in the material are dependent on c/a. Surface magnetization measurements show that for this sample each variant is dominated by a single direction of magnetization, with a change in magnetization at the twin boundary. Using a constrained sample technique, the rnagnetocrystalline anisotropy was measured at 0.16 MJ/m3, and the permeability was measured at 22 along the easy axis of the crystal and 2.1 along the hard axis. A model is proposed which predicts a threshold type strain behavior both with internal field at constant stress, and with stress at constant internal field. An experimental apparatus was built to test these conditions. The predictions of the model were largely verified in experiment and field-induced strains up to 6.1 % are measured. Blocking stress matched that predicts at about 1. 7 MP a A prototype magnetic actuator based on Ni-Mn-Ga was built to demonstrate the feasibility of the technology. lbis actuator applied fields of up to 600 kNm to a slender sample in the transverse direction. A maximum deflection of 1.6 mm is achieved for an active material length of 41 mm. AC testing shows the response degrades at frequencies above a few Hz. / by Steven J. Murray. / Ph.D.

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Materials Science and Engineering, 2017. / Cataloged from PDF version of thesis. / Includes bibliographical references. / Nanostructuring is an established method in engineering materials due to exciting new properties that manifest only in the nano-regime. When investigating nanomaterials, atom-scale simulations can be powerful tools. Through computational approach, one can 1) understand the underlying physics of a materials property, 2) propose new design principles for certain applications and 3) evaluate the performance of the material. In this thesis, we explore new materials and engineering approaches for various fields of application through a number of computational methods - molecular dynamics, density functional theory, semi-classical Boltzmann theory and Monte Carlo simulations. We first investigate the thermal and electrical transport properties of rippled graphene structures. Here we focus on the rippled textures formed by topological defects of graphene, namely Stone-Wales defects and graphene nanobuds. By exploring different configuration of Stone-Wales defects, the effect of rippling on the thermal conductivity is isolated. We also calculated the thermal and electrical transport properties of rippled graphene nanobuds and evaluate their thermoelectric efficiency. While looking into practical approaches to achieve two-dimensional materials with periodic nanostructures, our interest has extended to covalent organic frameworks (COFs) and their desalination properties. Through classical calculations, we show that COF membranes can achieve high salt rejection rate while enhancing the water permeability up to two to three orders of magnitude compared to conventional desalination membranes. The COF membrane was also shown to have decent mechanical properties although further modification may be needed to ensure its mechanical integrity in practical settings. Another type of self-assembled frameworks is the metal-organic frameworks (MOFs). Here the gas adsorption properties of MOF in defective and strained structures have been explored. We first look into water adsorption properties of MOF-801 and explore the role of defects. The defect sites contribute to preferential adsorptive behavior, which changes the water adsorption isotherm significantly. In addition, we look into strained UiO-66 structures and reveal that compressed, asymmetrical pores can affect the adsorptive behaviors of methane and carbon dioxide. This dissertation consists of five chapters. Chapter 1 first covers the general overview of the fields of application in concern: thermal and electrical properties of graphene-based systems, desalination, gas adsorption. Chapter 2 focuses on theoretical methods used for calculating thermal transport properties, electrical properties, desalination properties, and adsorption properties of materials of interest. Our results for the thermal and electrical transport properties of rippled graphene structure are presented in Chapter 3. In Chapter 4, we switch gears to calculate the desalination properties of two-dimensional covalent organic frameworks. Lastly, the gas adsorption of metal organic frameworks is discussed in Chapter 5. / by Jongwon Choi. / Ph. D.

Thesis (B.S.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1988. / Includes bibliographical references. / by Audrey M. Davis. / B.S.

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2004. / Includes bibliographical references (leaves 28-29). / This research focused on methods for regulating arrangement of self-assembled block copolymers by understanding fabrication conditions and their effects on the polymers on flat and patterned substrates. Block copolymer self-assembly is a simple and low cost process for creating lithographic masks with features under 100nm in dimension. These patterns can be transferred to more permanent materials for applications in electronics, magnetic devices, as well as sensors and filters. Polystyrene-poly(ferrocenyldimethylsilane) block copolymer thin films were characterized in terms of their spin curves, PSF spherical domain cross sectional area distributions, and correlation distances. Optimal fabrication conditions were selected from studying polymer behavior on flat substrates and then used for templated substrate studies. Substrates that were templated with grooves produced quantized numbers of rows of spherical domains ranging from 4 to 7. Behavior in these grooves was characterized in terms of groove width constraints, cross sectional domain area distributions, and row ordering. For all templated arrays, the lengths of ordered regions were more than 2 fold higher than the diameters of ordered regions of arrays on flat substrates. The characterization accomplished in this work will be used to compare block copolymers with similar volume fractions of the blocks that allow sphere microdomain formation but of different molecular weights. The ultimate goals are to establish how the molecular weight of this block copolymer affects its self assembly on templated and on flat substrates and to use this factor as well as fabrication conditions and template geometries to engineer arrays with desirable properties. / by Marianna Shnayderman. / S.B.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2007. / This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections. / Includes bibliographical references (v. 2, p. 375-377). / The Early Iron Age (750-450 BCE) marks a time in the European Alpine Region in which cultural ideologies surrounding bronze objects and bronze production were changing. Iron was becoming the preferred material from which to make many utilitarian objects such as weapons and agricultural tools; this change can be clearly seen in the different treatments of bronze object deposits from the Late Bronze Age to the Early Iron Age. The Early Iron Age hillfort settlement of Sticna in what is now southeastern Slovenia was one of the first incipient commercial centers to take advantage of the new importance placed on iron, conducting trade with Italy, Greece, the Balkans, and northern Europe. This metallurgical study of bronze funerary objects from Sticna identifies construction techniques, use patterns, and bronze metallurgical technologies from the ancient region of Lower Carniola. This information is then used to explore the cultural importance of bronze at Early Iron Age Sticna and to compare the bronze work of Lower Carniola with that of other regions in central Europe and Italy from this time of great change in Iron Age Europe. / S.M.

Thesis (M.Eng.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2002. / Includes bibliographical references (p. 85-89). / An investigation was completed to assess the viability of a group of metallic microfabrication techniques aimed at the production of microelectromechanical systems (MEMS) This undertaking was done to show which methods hold the most promise for the near future. The methods investigated include LIGA, micromilling, jet molding, three dimensional printing, microcasting, micro-injection molding, metal injection molding, Microforming, and microextrusion. This study presents a technique overview, assembly issues, an applications survey, basic cost modeling and a survey of the relevant intellectual property. / by Abel Z. Hastings. / M.Eng.

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Materials Science and Engineering, 2017. / This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections. / Cataloged from student-submitted PDF version of thesis. / Includes bibliographical references (pages 139-150). / Sulfur is a promising positive electrode for lithium batteries with the potential to create the step-change improvement in energy density and cost needed for the widespread adoption of electric vehicles and renewable energy. However, lithium-sulfur batteries suffer from a number of challenges, among them poor rate capability resulting in part from a complex dissolution-precipitation mechanism which produces electronically insulating end members S₈ and Li₂S. Few studies have heretofore been performed on rate-limiting mechanisms in Li-S batteries, which must be elucidated in order to inform rational design of electrodes with high capacity and rate capability. Polysulfide solutions, intermediates in the electrochemical reduction of sulfur, are used for the first time to make an efficient, high energy density flow battery, enabled by a novel flow battery architecture using a percolating network of nanoscale conductive carbon. An extensive experimental study of exchange current density for redox of higher order polysulfide solutions and their ionic conductivity has been conducted. The type and amount of electrolyte solvent has been found to influence both of these. The second portion of this thesis characterizes the kinetics of Li₂S electrodeposition, which is responsible for three-quarters of the theoretical capacity of the sulfur cathode. Kinetics are found to be highly dependent on solvent choice in a manner similar to exchange current density. Furthermore, electrodeposition kinetics are found to slow considerably at the low electrolyte/sulfur ratios which are needed for high energy density and low cost. Materials such as conductive oxides can serve as nucleation promoters and help solve this challenge. The morphology of precipitates is found to be dependent on discharge rate, with large, discrete particles forming at low rates. A model was for describing 3-D electrodeposition of Li₂S under the influence of a soluble redox mediator which enables efficient utilization of conductive surface area and prevents passivation of conductive carbon with insulating Li₂S. / by Frank Yongzhen Fan. / Ph. D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1996. / Vita. / Includes bibliographical references (leaves 126-128). / by Linda K. Molnar. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1995. / Includes bibliographical references. / by Elliot M. Schwartz. / Ph.D.